City planning to stabilize Ralston Creek

IOWA CITY - Normal erosion coupled with some recent flash flood episodes are taking their toll on the banks of Iowa City's Ralston Creek.

To address severe erosion on the east and west banks of roughly three blocks of Ralston Creek between Muscatine Avenue and Sheridan Avenue, officials with the Iowa City Engineering Department are recommending a roughly $180,000 creek stabilization project to reinforce about half of the area in need.

Erosion has caused undercutting of the bank slopes, loss of trees and property and increased risk of damage to nearby property, according to the city document recommending the project.

City Engineer Ron Knoche said most of the erosion has been caused by normal water flow in the creek, but added that recent flash floods, which occurred earlier this summer and in April 2013, have made matters worse.

'You do have the situation where you have the big rain events that we've had, we're getting more erosion going on,” he said.

The Iowa City Council will vote Tuesday on setting a public hearing Nov. 4 on the first phase of project, with city staff hoping to eventually open the project for bids and award the contract Dec. 2.

Phase two would finish the project, but Knoche said funds have not yet been identified for the second half of work.

Phase one of the project - to be funded by roughly $30,000 in Federal Emergency Management Agency dollars while the rest will come from the city's stormwater utility fund - addresses erosion issues from Muscatine Avenue to south of Center Avenue.

Work to stabilize the banks includes clearing debris, reshaping and re-establishing bank slopes, armoring the banks with stone and installing riffle pools to reduce water flow velocity.

'It will kind of slow that flow down and hopefully alleviate some of the washout and erosion that occurs with higher velocity flows,” said Jason Reichart, special projects engineer.

Reichart added that winter, with less water in the creek and a slower current, will make for the best time to start working.

'The less water you have to deal with, the better,” he said. 'Ideally you'd like to have everything in place by the spring so if we have a lot of rain or flash flooding we're prepared for it.”